In the petroleum refining process coker heaters are used to heat vacuum bottoms being refined in order to form gas, gas oil, and petroleum coke. One of the more common types of coker heaters is a double fired coker heater. The double fired coker heater of the prior art typically has one or more tube bundles located within the radiant section of a heater. One or more burners are located on each side of the tube coil. The burners provides the radiant heat to heat the fluid passing through the tube bundle.
The prior art tube bundles have a single flow path with tubes and fittings creating a serpentine pattern. The fluid being heated is allowed to pass through this coil while the burners provide the radiant heat source.
Oil refineries are complex facilities often times with very limited space. Over the years as a refinery is expanded, the competition for this limited space becomes ever increasing. One of the drawbacks of the prior art tube design is that it requires an excessive amount of area to locate the coker heater. Each serpentine coil arrangement contains only one process pass. This means a separate coil (line of tubes) must be added for each pass. As the number of coils increase so does the size of the coker heater and the area need to locate the coker heater.
One of the factors that complicates this situation is that the coker heater must be in relative close proximity to the coke drums. If the coker heater is located too far away from the drum the pressure drop associated with the transfer line can become excessive. Increasing the outlet pressure of the coker heater increases the rate of fouling and reduces the run length. Often times additional space is available at the refinery, however it is too far from the coke drums to be a suitable location for a coker heater.
What is needed is a tube coil design which allows for a more compact coker heater.
Hence what is needed is a coker heater and tube design which can have increased heater capacity with reduced area or footprint.
Another drawback to the prior art tube bundles is that they lead to larger coker heaters. In addition to taking up more space they are also more expensive to construct and operate.